Why does Duncan trust Macbeth and Lady Macbeth?

Thesis. In Macbeth, it is certain that a king should not excessively believe and fully trust his thanes.

Supporting Ideas.
1. The former thane of cawdor had betrayed King Duncan and fled to Norway to help them defeat Scotland.

ANGUS (1.3 line 109-116)

Who was the thane lives yet,But under heavy judgment bears that lifeWhich he deserves to lose. Whether he was combinedWith those of Norway, or did line the rebelWith hidden help and vantage, or that with bothHe labored in his country’s wrack, I know not;But treasons capital, confessed and proved,Have overthrown him.

2. Macbeth, the respected thane of King Duncan, also betrayed his loyal king through assassinating the king.

Enter MACBETH, with bloody daggers
My husband! (Lady Macbeth)
MACBETH (2.2 line 15)

I have done the deed.(killed King Duncan) Didst thou not hear a noise?

3. Macduff who was under Macbeth had betrayed him and later defeated him with the army of England.

(3.6 line 29)
Thither MacduffIs gone to pray the holy king upon his aidTo wake Northumberland and warlike Siward,That by the help of these—with Him aboveTo ratify the work—we may againGive to our tables meat, sleep to our nights,Free from our feasts and banquets bloody knives,
Do faithful homage and receive free honors.